The combination of Cisplatin and S-1 (CS) achieved a response rate of approximately 45% with the PFS being around 6 months and overall survival time being 13 months in Japanese and Chinese gastric patients. It remains unclear whether the addition of docetaxel to CS would further enhance the efficacy as it dose in DCF(docetaxel, cisplatin and 5-fluorouracil). This is a single center, phase II clinical trial to evaluate the efficacy of docetaxel, cisplatin and S-1 (DCS) as first line chemotherapy for patients with advanced gastric and gastroesophageal junction cancer.